Immunization of BALB/c or CB6F[unreadable]1[unreadable] mice to heterologous erythrocytes induces multiple regulatory T cells that can initially be segregated by their ability to selectively modulate either clone growth or secretory differentiation of the anti-TNP IgA-secreting BALB/c myeloma MOPC-315 in the presence of TNP-conjugated heterologous erythrocytes. The target for both the proliferation and differentiation helper and suppressor T cells appears to be the small, nonsecretory lymphocytoid MOPC-315 tumor stem cells. The purpose of the experiments is to produce monoclonal lines of each helper and suppressor T cell induced by sheep erythrocyte immunization of CB6F[unreadable]1[unreadable] mice and to characterize each monoclonal regulatory cell as to its triggering requirements for proliferation and regulatory factor secretion, specificity of cell surface receptors, cell cycle alterations in receptor expression, and regulatory factor secretion. In past year we have successfully produced three helper T-cell hybridomas which constitutively secrete a light chain idiotope [unreadable]315[unreadable]-specific helper factor that induces secretory differentiation of virtually all of the MOPC-315 cells, even a density gradient-purified nonsecretory 315-cell subpopulation. These hybridomas were produced by fusing SRBC-immune Ly 1 T cells, which adhered to IgAlambda[unreadable]2[unreadable] [unreadable]315[unreadable]-coated Petri plates, with HGPRT[unreadable]-[unreadable] BW5147 T lymphoma cells and then selecting for hybrids by growth in HAT media. Cultures positive for 315-cell differentiation help, but those which did not enhance 315-cell proliferation were cloned by limiting dilution. Similarly, two cloned suppressor T-cell hybridomas which suppress MOPC-315 cell secretory differentiation but have no effect on 315 cell growth have been produced. One of these specifically binds alpha-[unreadable]315[unreadable]idiotopes while the other is SRBC specific. I have also produced a cloned contrasuppressor I-cell hybridoma which is specific for SRBC. This hybridoma makes 315 cells resistant to the IgA [unreadable]315[unreadable]-binding T[unreadable]S[unreadable] cell-secreted factors but has no helper activity itself. I am in the process of phenotyping these T-cell hybridomas using flow cytometry and am beginning to purify, by affinity chromatography, the IgAlambda[unreadable]2[unreadable] [unreadable]315[unreadable]-specific regulatory factors produced. I am also determining whether IL-2, IL-3, and gamma-interferon are secreted by any of these hybridomas and am beginning to develop normal cloned lines of these types of T cells. (LB)